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- Author or Editor: W. Liu x
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Abstract
This study investigated the community structure of ciliates in Gahai Alpine Wetland of Qinghai-Tibetan Plateau, China. We hypothesized that the ciliate community in the Plateau is more complex and the species diversity is richer than those in other climate zones of China. In particular, we studied how the ciliate species responded to environmental temperature, soil moisture content and the manner of pasture utilization. We determined key features of the ciliate communities such as trophic functional groups, ciliate seasonal distribution, species diversity and similarity index at six sample sites from January 2015 to October 2016. To count and characterize ciliates, we combined the non-flooded Petri dish method with in vivo observation and silver staining. We identified 162 ciliate species in this area, showing a high species and functional diversity. The mode of nutrition was diverse, with the lowest number of ciliates in group N (Nonselective omnivores, 4 species) and the highest number in group B (Bacterivores-detritivores, 118 species, corresponding to 73% of the total species number). Ciliate species richness was significantly positively correlated with environmental temperature and moisture and adversely related to the intensity of agricultural land use. Rotational grazing by livestock or suspended grazing might be useful for maintaining good soil quality, thereby favoring ciliate diversity. Our study may serve as a reference to evaluate the ecosystem status of the Gahai Alpine Wetland and other similar areas in future studies.
Wheat kernel morphology is a very important trait for wheat yield improvement. This is the first report of association analysis of kernel morphology traits in wheat breeding lines. In Qinghai, China, the research described here involved genome-wide association analysis in breeding lines derived from synthetic hexaploid wheat with a mixed linear model to identify the quantitative trait loci (QTLs) related to kernel morphology. The 8033 effective Diversity Array Technology (DArT) markers produced a genetic map of 5901.84 cM with an average density of 1.36 markers/cM. Population structure analysis classified 507 breeding lines into three groups by Bayesian structure analysis using unlinked markers. Linkage disequilibrium decay was observed with a map coverage of 2.78 cM. Marker-trait association analysis showed that 15 DArT markers for kernel morphology were detected, located on nine chromosomes, and explained 2.6%–4.0% of the phenotypic variation of kernel area (KA), kernel width (KW), kernel length (KL) and thousand-kernel weight (TKW). The marker 1139297 was related to both the KL and KA traits. Only six DArT markers were close to known QTLs. The parent SHW-L1 carried eight favored alleles, while other seven favored alleles were derived from elite common wheat cultivars. These QTLs, identified in elite breeding lines, should help us understand the kernel morphology trait better, and to provide germplasm for breeding new wheat cultivars for Qinghai Province or other regions.
We present a new method to asses the strength of indirect interactions and to indentify candidate keystone species in quantitative food webs. We apply this method to the structural analysis of a host-parasitoid community. The strength and symmetry of indirect interactions between 12 leaf-miner hosts and their 27 hymenopteran parasitoids are quantified. It is shown that (1) quantifying longer pathways helps in determining which species have more important direct or indirect effects on others, (2) a keystone pattern of relative species importance, based on positionality in the interaction network, seems to characterize this community, (3) considering longer pathways results in a characteristic “few strong - many weak” distribution of interaction strength, and (4) between the majority of species pairs the interaction is weakly asymmetrical. We emphasise that a very simple network algebra approach may offer important predictions on both species- and community-level patterns.
Stem rust caused by Puccinia graminis f. sp tritici of wheat (Triticum aestivum L.) is one of the most destructive cereal diseases globally. Concern about the disease has increased since 1999 with the discovery in Uganda of a new virulent race of Pgt, designated as race TTKSK (also known as Ug99). The objectives of this experiment were to characterize the resistance and to determine the chromosomal location of the stem rust resistance in the spring wheat line PI 410966. A mapping population was developed from a cross between PI 410966 and a susceptible wheat line OK3040. An inoculation test with isolate 04KEN156/04 of race TTKSK was conducted at the USDA-ARS Cereal Disease Laboratory in the F6:7 generation, and the F6:7 phenotypic data were used to genetically map the resistance gene to the centromeric region on chromosome 2BS. The single locus explained the observed F6:7 resistant and susceptible scores. The location of the gene and molecular marker banding profiles of the diagnostic markers suggest that the stem rust resistance gene in PI 410966 could be a new gene, an allele of Sr36, or Sr36.
Wheat glutenins containing high and low molecular weight glutenin subunits (HMW-GS and LMW-GS) are the major determinants of wheat gluten quality. In this study, the recently developed reversed-phase ultra-performance liquid chromatography (RP-UPLC) was used to study the synthesis and accumulation patterns of glutenins during grain development of four Chinese bread wheat cultivars with different gluten quality. Developing grains were collected based on thermal times from 150 °Cd to 750 °Cd at 100 °Cd intervals, and the content of glutenin subunits and their accumulation patterns were determined by RP-UPLC as well as sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The results showed that HMW-GS and LMW-GS synthesis were initiated currently at 250 °Cd and they displayed a gradually upregulated expression. All the HMW-GS can be detected at 250 °Cd, earlier than LMW-GS. Different glutenin subunits and genotypes showed clear accumulation diversity during grain development. Particularly, 1Dx5 + 1Dy10 in the cultivar Gaocheng 8901 and Zhongyou 9507 with superior dough properties were accumulated faster at early stages than 1Dx2 + 1Dy12 in Jingdong 8 and Zhengmai 9023 with poor dough quality, suggesting that faster accumulation rate of glutenin proteins at the early stages of grain development may contribute to the formation of superior gluten structure and dough quality.
Glutenin subunit alleles at the Glu-D3 locus and their effects on dough properties, pan bread, and dry white Chinese noodle (DWCN) qualities were investigated using 106 winter and facultative wheat cultivars and advanced lines. Allele Glu-D3c (42.5%) was the most frequent glutenin subunit, followed by Glu-D3b (25.5%) and Glu-D3a (23.6%). Glu-D3d and Glu-D3f occurred in only three and six cultivars, respectively. The effect of Glu-D3 was significant forDWCNquality, accounting for up to 16% of the variation, but there were no significant differences between individual Glu-D3 alleles on dough properties and qualities of DWCNand pan bread. Interaction effects Glu-A1 × Glu-D3 and Glu-B1 × Glu-D3 were significant for DWCN quality and loaf volume. More work is needed to understand the effects of Glu-D3 variation on the determination of dough properties and end-use quality.
In this study, the cDNA of homocysteine S-methyltransferase was isolated from Aegilops tauschii Coss., with the gene accordingly designated as AetHMT1. Similar to other methyltransferases, AetHMT1 contains a GGCCR consensus sequence for a possible zinc-binding motif near the C-terminal and a conserved cysteine residue upstream of the zinc-binding motif. Analysis of AetHMT1 uncovered no obvious chloroplast or mitochondrial targeting sequences. We functionally expressed AetHMT1 in Escherichia coli and confirmed its biological activity, as evidenced by a positive HMT enzyme activity of 164.516 ± 17.378 nmol min−1 mg−1 protein when catalyzing the transformation of L-homocysteine. Compared with the bacterium containing the empty vector, E. coli harboring the recombinant AetHMT1 plasmid showed much higher tolerance to selenate and selenite. AetHMT1 transcript amounts in different organs were increased by Na2SeO4 treatment, with roots accumulating higher amounts than stems, old leaves and new leaves. We have therefore successfully isolated HMT1 from Ae. tauschii and characterized the biochemical and physiological functions of the corresponding protein.
Prorocentrum donghaiense caused large-scale red tides off Chinese coast in recent years. Expressed sequence tag (EST) analysis was carried out for this dinoflagellate in order to identify the genes involved in its proliferation and death. A cDNA library was constructed for P. donghaiense at late exponential growth phase, and 308 groups of EST were generated, which include 36 contigs and 272 singletons. Among 22 groups showed homologies with known genes, 2 matched significantly with caspase and proliferating cell nuclear antigen. Caspase and proliferating cell nuclear antigen are 2 key proteins involved in programmed cell death. Their identification evidenced preliminarily the induction of PCD in aging P. donghaiense. The identified included also calmodulin and protein phosphatase, two proteins involved in diverse cell processes including PCD by binding to or modifying others.
Purple pericarp is an interesting and useful trait in Triticum aestivum, but the molecular mechanism behind this phenotype remains unclear. The allelic variation in the MYB transcriptors is associated with the phenotype of pigmented organs in many plants. In this study, a MYB transcription factor gene, TaMYB3, was isolated using homology-based cloning and a differentially expressed gene mining approach, to verify the function of the MYB transcriptor in the purple pericarp. The coding sequence of TaMYB3 in cultivar Gy115 was the same as that in cultivar Opata. TaMYB3 was localized to FL0.62–0.95 on chromosome 4BL. The TaMYB3 protein contains DNA-binding and transcription-activation domains, and clustered on a phylogenetic tree with the MYB proteins that regulates anthocyanin and proanthocyanin biosynthesis. TaMYB3 localized in the nuclei of Arabidopsis thaliana and wheat protoplasts after it was transiently expressed with PEG transformation. TaMYB3 induced anthocyanin synthesis in the pericarp cells of Opata in the dark in collaboration with the basic helix–loop–helix protein ZmR, which is also the function of ZmC1. However, TaMYB3 alone did not induce anthocyanin biosynthesis in the pericarp cells of the white grain wheat cultivar Opata in the light after bombardment, whereas the single protein ZmR did. Light increased the expression of TaMYB3 in the pericarp of Gy115 and Opata, but only induced anthocyanin biosynthesis in the grains of Gy115. Our results extend our understanding of the molecular mechanism of the purple pericarp trait in T. aestivum.
Red coleoptile is an easily observed agronomic trait of wheat and has been extensively studied. However, the molecular mechanism of this trait has not yet been revealed. In this study, the MYB gene TaMYB-D1 was isolated from the wheat cultivar ‘Gy115’, which possesses red coleoptiles. This gene resided at the short arm of the homoelogous group 7 chromosomes. TaMYB-D1 was the only gene expressed in the coleoptiles of ‘Gy115’ and was not expressed in ‘Opata’ and ‘CS’, which have uncoloured coleoptiles. Phylogenetic analysis placed TaMYB-D1 very close to ZmC1 and other MYB proteins regulating anthocyanin biosynthesis. The encoded protein of TaMYB-D1 had an integrated DNA binding domain of 102 amino acids and a transcription domain with 42 amino acids, similar to the structure of ZmC1. Transient expression analysis in onion epidermal cells showed that TaMYB-D1 was located at the plant nucleus, which suggested its role as a transcription factor. The expression of TaMYB-D1 was accompanied with the expression of TaDFR and anthocyanin biosynthesis in the development of the coleoptile of ‘Gy115’. Transient expression analysis showed that only TaMYB-D1 induced a few ‘Opata’ coleoptile cells to synthesize anthocyanin in light, and the gene also induced a colour change to red in many cells with the help of ZmR. All of these results suggested TaMYB-D1 as the candidate gene for the red coleoptile trait of ‘Gy115’.
